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to crystallisation as before. The sodium naphthalene sulphonatc
is separated by filtration, and dried in a basin on the water-bath.
The mother-liquor, on evaporation, yields a further quantity of
the salt. Yield, about 60 grains.

1.     (',,,11,+ ILSO.,-CtoH7S< UI + TU).

2.    2C:IOI I7S( >.,! I + CaO - (C10I l7SO,),Ca+ 1LO.

rwpcrtics.......Koliated     crystals;    soluble    in     water.      See

ppendix, p. 315.


p-Naphthol, C,0!17.OH

Kllcr, Atiim/fti, 1869, 152, 275 ; K. l'ischcr, Anlcitung s. d.
rg. rrtipiti'titc.

30 ijnns. /^-naphthalene sulphonatc of sodium.
90          i'austic sod:i,

The caustic soda and water arc; heated in a nickel fir silver
crucible, and stirred with a thermometer, protected as described                        W
under the preparation of phenol (p. 179).    When the temperature                       V-
reaches 2So', the powdered naphthalene sulphonate is added a                      JM'.I
little at a time.    When all has been added, the temperature is                      '.^t
raised.    At about  300" the mas-s froths up  and  becomes li^'ht
yellow  in  colour,  which  indicates   the   commencement   of the                         r!
reaction.    The temperature is  maintained at. 3io-~32o': for a                      s * '
few minutes, and the end of the process is  indicated by the                      ' i L
yellow mass becoming thinner and also darker in colour, and                       *i
separating into two layers.    The stirring  is now stopped and                        ff
the (lame withdrawn.     The product, when cold, is dissolved in          t            l j'|J
H little water, rind acidified with a, mixture of equal volumes of                      ' |
concentrated hydrochloric acid and water.*                                                        tf;
The naphthol is filtered, off when cold, and is recrystalliscd                       l|
from water.    Meld, 15 grains.                                                                              i tf
Cj0ll7S< )3Na -H NaOH - C10I I7(JNa, + Na I ISO.,.                                  ^
Colourless leaflets ; m. p. i22r; ; b. p. 286'.                                  ^